Liner for rubber sheeting



May 19, 1953 E. GURIN ETA.

LINER FOR RUBBER SHEETING Filed April 26, 1949 Patented May 19, 1953 Emamlel (urinfaudslarl Fox, n

fsianersatpiltanidiltller Companmlimagaflll The present invention relates :'to a liner for rubber material, and-toa process Lfon--makingethe same.

Inf-.p articular, #the invention-relates to i a `coated :fab/rictcomposition which ern-ay-Qbe insertedf-'bemember so that tthe rubbensheetlrnayibe sto-red .'indeff-lnitelyl Vand smay l'beeasily-fstnipped ffrorn ythe .backing membenwthoutftherubberstckinguunduly-thereto. 1 i f f .Tit :has 'been Afound lthat when rubber sheets are vcoiled for purposes of storage `rwith rubber surfaces nbeing separated uby an ordinary 1fabi-ic, or; commeiici-ally treated diner, it '-isdiicult gifynot impossible -to fstrip'the rubb er lsheets-naterialgrom the backing cloth-memberwithoutlinjury:to the rubber-'sheet Jhisf-is-especially true in the case of synthetic rubbers which contain ester and other typesef plastieizers- This eet may be dueto the --migration offthe plasticizer from the rubber into the liner :materiahpr .the affecting of therubber sheeting by ,materials in the rliner ,coating gra purely physical ,attraction ,of `)liner k.and rubbelrsheeting.

fAhobject-01? the presentinvention is to ,provide a lineradapted to be insertedibetween slieetsof grabber material t permit fsilprmposing auch rubbersheets vvithoutthe.` ub materia l5- in'gQundulyto the surface ci er 'A further object of thewpr provide a liner-material wh may be used as backing vsurface for sheets of 'synthetic frubber @emirats ester tree :nlasticiaersicapahle ,of treettillg-ztheinlsrationscfitbc plasticizeryfriomethe rubber material to the liner.

Another object of the present invention is to provide a method for the production of a coated Woven fabric suitable for use as a liner for rubber sheets.

In accordance with the present invention, a Woven fabric, such as duck, is treated with a fluid coating composition containing as essential ingradients, polyvinyl butyral and an acetal forming compound, such as an aldehyde or an aldehyde forming compound, for example, formaldehyde, glyoxal, furfural, paraformaldehyde, and the like. An especially preferred aldehyde forming compound is hexamethylenetetramine. These compounds undergo a reaction under the influence of heat and set to a non-tacky but pliable coating on the surfaces of the fabric. The nature of the reaction is not completely understood, but it is believed that the aldehyde group reacts With free hydroxyl groups present in the ntinvention 1s to Chicago, Ill., as-

.at the este@ tf1 th siem/S @are ai, man sartene@ tbe-Mercurial@ ab has he :te be an excellent Xbaclslesfssrfaqe ferent l cir-nat afcsifiiinsiiedtv a si plastici/Zeit, ses the e the surface of the fabric, We @cette with ita@ @up agents ,weicht-r te ille @inst-more Watsnelaeilaei than@ amore-ip 1e. auch {ripetersi-.ed assume 'phenol-.formaldehyde condensatignprgdno A legalcolhol ,estimator-1;@- "lbis staseef tismnroduct is "15me eipbnolf prefer to integre @d amaramente nher ,Ebates also as teeth 0 [eheseliata @een @sieht-:ns1 phosphate, istlesehate@perennials/tes asedif methyl phthalate, diethyl phthalate, dibutyl phthalate, diamyl phthalate, and dihexyl phthalate. In addition, various other ester type .plasticizers, such as for example, methyl abietate, triethyl citrate, tributyl citrate, butyl ricinoleate. dimethyl sebacate, dibutyl sebacate, butyl laurate, amyl laurate, castor oil, and butyl oleate, may be used.

The preferred solvents to be used in compounding the coating are alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, and isobutyl alcohol, and the aromatic hydrocarbons such as toluene and xylene. Preferably, the solvent is a mixture of both types of parts by weight of polyvinyl butyral 0 to 200 parts by Weight of an alcohol-soluble phenol-formaldehyde resin 100 parts by weight of polyvinyl butyral 25 parts by weight of hexamethylenetetramine 10 parts by weight of dibutyl phthalate An especially preferred formula is the following:

100 parts by Weight of polyvinyl butyral 20 parts of an alcohol-soluble phenol-formaldehyde resin parts by weight of hexamethylenetetramine parts by Weight of dibutyl phthalate 200 part-s by weight of ethyl alcohol 200 parts by weight of toluene The coating is applied to one or both surfaces of the woven fabric in an amount such that the coating constitutes from about 20 to 200% by weight of the finally coated fabric. The coated fabric is next dried at a moderate temperature sufficient to volatilize the solvents present. Normally, this temperature will be less than about 200 F. After volatilization of the solvent, the coated fabric is next subjected to rather elevated temperatures, normally on the order of 300 to 350 F. for the purpose of setting and. curing the composition to a non-tacky layer or film firmly bonded to the surfaces of the fabric.

The present invention will further be described in connection with the description of the attached sheet of drawings, in which:

Figure 1 is an end view of a laminated structure comprising a sheet of rubber material and a treated liner rolled together into the form of a coil;

Figure 2 is an enlarged fragmentary view of a section of the coil shown in Figure 1; and

Figure 3 is a cross-sectional view of the liner and a sheet of rubber material placed thereon.

Asshown on the drawings:

The reference numeral I0 denotes in general a roll or coil of a sheet or web of rubber material I I with the successive windings thereof separated by a liner I2. The liner I2 consists of a Woven fabric body of interwoven strands I3 having a coating I4 impregnating the fabric body and enveloping the strands I3. As shown in Figure 3, the strands I3 provide a rough outer surface to the fabric, which facilitates adhesion of the coat- 4 ing to the fabric and also facilitates the stripping of the rubber material from the coated fabric due to the airpockets I5 therebetween.

The liners of the present invention have been found to be especially suitable for use in connection with synthetic rubber compositions such as copolymers of butadiene and acrylonitrile, or of butadiene, acrylontrile and styrene, and containing ester type plasticizer, although it can be used with natural and all types of synthetic rubber. The insertion of a liner of the type herein disclosed between alternate sheets of the rubber material prevents deterioration of the surface of the rubber sheets, even after prolonged storage. While adhering lightly to the surfaces of the liner, the rubber sheet may nevertheless be readily stripped therefrom without any of the rubber material being left stuck to the liner or vice versa. Instead of being wound up into a roll the rubber sheets and liners may be laid flat in superimposed relation in a stack.

We claim as our invention:

As a new article of manufacture, a laminated structure comprising alternate layers of a coated fabric liner and of a synthetic rubber selected from the group consisting of copolymers of butadiene and acrylonitrile and of copolymers of butadiene, acrylonitrile and styrene, said fabric liner being coated on both sides with a cured polyvinyl butyral composition comprising the reaction product of parts by Weight of polyvinyl butyral, an acetal forming compound equivalent vto from 5 to 25 parts by weight of hexamethylenetetramine and an ester type plasticizer, whereby said rubber layer may be readily stripped from said liner without portions of said synthetic rubber layer being left stuck thereto.

EMANUEL GURIN. KARL FOX.

References Cited in the Ile of this patent UNITED STATES PATENTS Number Name Date 1,749,743 Sebrell l Mar. 4, 1930 2,201,537 Hickler May 21, 1940 2,268,121 Kingsley Dec. 30, 1941 2,387,831 Cogan et al Oct. 30, 1945 2,409,548 Debacher Oct. 15, 1946 2,430,931 Hershberger Nov. 18, 1947 2,441,542 Lawrence May 11, 1948 FOREIGN PATENTS Number Country Date 574,459 Great Britain Jan. 7, 1945 573,437 Great Britain Nov. 21, 1945 

